Investigating Of Embedded SIP Phone Based On ARM9

With the development of network, embedded and communications technology, and it is increasingly application of 3G&NGN concept, the number of organizations on researching SIP technology and embedded communication network equipment are also increased rapidly. As the VoIP technology developed by IETF, SIP is one of the most important signaling protocols. Distributed control mode is adopted by SIP protocol, providing integrated multimedia services. Its good scalability, mobility and media consultation ability are good for improving network interoperability and openness of embedded devices. For these goals, we are attempting to combine with embedded systems and SIP technology and to design an ARM9-based embedded SIP phone terminal.This paper analyzes the functional structure of the SIP, the message mechanism, the SDP and other related technologies. Standing on these technologies, we implement the SIP telephone terminal on embedded system. A powerful ARM9 chip-S3C2410X is used to construct the core of the terminal, which adopts embedded Linux as the underlying operating system. The core work include the implementation of SIP protocol stack, voice coding and decoding, embedded Linux porting and the SIP UA developing based on SIP protocol stack specification. The terminal implements the voice collection, coding, recoding and playback by the audio interface, implement network transmission of signaling and voice by Ethernet interface. It implements SIP user agent, user registration, initiated conversation, terminate conversation, conversation response and other functions, supports SPEEX, G.711 and G.729 voice coding method. Finally, according to the design objective, the consistency, interoperability and performance of the terminal are tested. Test results show that the embedded SIP phone terminal in this paper is corrects both in design project and development process.